The present invention is in the field of thermal (infrared) target simulators. In order to train operators in the use of thermal target viewers, either real or simulated targets which one might encounter when using such a viewer must be provided. In the case of a tank or some other large target, it may be impractical to use the real thing. Various schemes have been proposed to date which simulate targets to more or less degrees. One interesting scheme is that shown by Vincent T. Bly in U.S. Pat. No. 4,178,514 of Dec. 11, 1979, wherein a visible image is converted into an infrared image by what Bly called a "visible to infrared transducer," but which is now known in the art as a "Bly cell." The infrared image thus obtained may be used to test infrared detectors, etc. Another scheme employs a mock-up of a target with heat sources therein to simulate target heat sources such as engines; U.S. Pat. No. 4,253,670 of Mar. 3, 1981 by Moulton et al shows this scheme.
Unfortunately, these prior art schemes suffer from the disadvantage that they are essentially two-dimensional simulations, i.e. one cannot look at the simulations from various aspects with a thermal viewer as one might be expected to do with a real target. Moreover, they cannot account for changes in the thermal signatures of targets for various conditions. In the case of a tank, its thermal signature depends upon such things as whether it has been moving recently (with subsequent heating of its drive sprockets, shock absorbers, bogie or road wheels, and tracks), whether its cannon or machine guns have recently fired, whether and how long its engine has been running, and whether or not its personnel heater is or has been recently in use. Further, the simulators thus far described use infrared sources or images to produce a simulated infrared target for an infrared viewer. In many instances, because of cost or availability, it is desirable to simulate an infrared image not on an infrared viewer, but by some other means. A television monitor is a good device for this, if one can generate a simulated infrared image for display on such a monitor. A method and apparatus for so doing is what this invention is concerned with. The invention as described herein provides a variable signature three-dimensional target simulation and thus overcomes the prior art disadvantages.